This invention relates to a process for polymerizing vinyl monomers, more particularly this invention relates to a process for polymerizing an aqueous solution of a .alpha.,.beta.-ethylenically unsaturated monomer to produce water-swellable polymer.
Such polymerizations are typically carried out using redox initiator pairs and crosslinking agents. Examples of typical crosslinking agents include diacrylate or dimethacrylate esters of ethylene glycol: triacrylates or trimethacrylates of trimethylol propane and others. The crosslink is formed when growing polymer chains react with the vinyl groups of the typical crosslinking agent. During such polymerizations it is thought that the free radical generated by the initiator, produces dangling chains of polymer which may lead to undesirable residual monomers and uncrosslinked polymer.
Polymers which form hydrogels are used in fluid absorbing products such as disposable diapers, incontinent devices and sanitary napkins and are well known in the art. These polymers are typically prepared by polymerization of .alpha.,.beta.-ethylenically unsaturated monomers with crosslinking agents. The development of improvements in the processes for preparing these water-swellable polymers is desirable to produce improved products, eliminate by-products and increase production capacity. The improvements in the processes however, should not sacrifice excellent free swell capacity and extractable polymer content properties of the polymer.